Tractor

ABSTRACT

A tractor including: a traveling body having an engine; a post-processing device configured to purify exhaust gas of the engine; and a reductant tank configured to store a reductant to be supplied to the post-processing device. A pair of left and right fuel tanks are arranged respectively on left and right sides of a longitudinally midway portion of the traveling body. A tank-accommodation recess for accommodating a reductant tank is formed at a lower-front portion of one of the left and right fuel tanks. While the reductant tank is accommodated in the tank-accommodation recess, an upper front portion of the fuel tank and the reductant tank are aligned up and down.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/235,121 filed Apr. 20, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/499,052 filed Sep. 27, 2019 (now U.S. Pat. No.11,007,869), which is a national stage application pursuant to 35 U.S.C.§ 371 of International App. No. PCT/JP2018/006135 filed Feb. 21, 2018which claims priority under 35 U.S.C. § 119 to JP Pat. App. No.2017-069275 filed Mar. 30, 2017, the disclosures of which are herebyincorporated by reference in their entireties.

DESCRIPTION Technical Field

The present invention relates to a tractor for agricultural work, andmore specifically, a tractor including a post-processing device forremoving particulate matters, nitrogen oxides, and the like contained inexhaust gas from an engine.

Background Art

Traditionally, a technology which purifies exhaust gas discharged from adiesel engine, by providing an exhaust path with a case having therein adiesel particulate filter (hereinafter, DPF case) and a case havingtherein a selectively reducing catalyst (hereinafter, SCR case), as apost-processing device (also referred to as exhaust gas purificationdevice), and introducing the exhaust gas discharged from the dieselengine into both cases (see for example Patent Literatures 1 and 2;hereinafter, referred to as PTL 1 and PTL 2, respectively) is known.

To remove nitrogen oxides in the exhaust gas through a selectivecatalytic reduction (SCR), a reductant (e.g., urea water) needs to besupplied. In order to mount an SCR denitration device to a tractor, aspace is needed for not only mounting the SCR case but also for mountinga reductant tank.

CITATION LIST

-   PTL 1: Japanese Patent Application Laid-Open No. 2016-203753.-   PTL 2: Japanese Patent Application Laid-Open No. 2016-74267.

In a tractor of the prior art, a pair of left and right fuel tanks arearranged respectively on left and right sides of a longitudinally midwayportion of the traveling body, and a reductant tank is arranged in frontof the left fuel tank. In other words, the left fuel tank and thereductant tank are aligned in the front and rear directions. For thisreason, for example, even if a large capacity of the left fuel tank isneeded, there is a limitation due to the longitudinal length of thetractor, and depending on the shape and the sizes of an operation unit(cabin) and steps may have to be sacrificed.

SUMMARY OF INVENTION

In view of the current circumstances described above, it is a technicalobject of the present invention to provide an improved tractor.

An aspect of the present invention is a tractor including: a travelingbody having an engine; a post-processing device configured to purifyexhaust gas of the engine; and a reductant tank configured to store areductant to be supplied to the post-processing device, wherein a pairof left and right fuel tanks are arranged respectively on left and rightsides of a longitudinally midway portion of the traveling body; atank-accommodation recess for accommodating the reductant tank isformed, at a lower-front portion of one of the left and right fueltanks; and while the reductant tank is accommodated in thetank-accommodation recess, an upper front portion of the one of the leftand right fuel tanks and the reductant tank are aligned up and down.

The tractor according to the above-aspect of the present invention maybe such that: a fueling cylinder protrudes upward from an upper surfaceat an upper front portion of the one of the left and right fuel tanks;and a supply cylinder protrudes obliquely upward and outward from anoutside surface of the reductant tank with respect to a left-rightdirection.

The tractor according to the above-aspect of the present invention maybe such that a reductant supply device for supplying the reductant inthe reductant tank is arranged between the traveling body and thereductant tank.

The above-aspect of the present invention may be such that: steps forgetting on and off an operation unit on the traveling body are arrangedsuch that one of them and the other of them are disposed on the left andright, respectively, and an auxiliary frame extended towards the one ofthe left and right fuel tanks having the tank-accommodation recess isprovided to the traveling body; and the reductant tank is supported bythe auxiliary frame and one of the steps on the side where the one ofthe left and right fuel tanks having the tank-accommodation recess isdisposed.

The present invention includes an aspect as described in claim 5.Namely, the aspect of the present invention described in claim 5 is atractor including: a traveling body having an engine; a pair of left andright front wheels and a pair of left and right rear wheels to supportthe traveling body; steps for getting on and off an operation unit onthe traveling body; a post-processing device configured to purifyexhaust gas of the engine; and a reductant tank configured to store areductant to be supplied to the post-processing device, wherein thereductant tank is arranged between one of the steps and one of the frontwheels, on one of the left and right sides of the traveling body; andthe front surface of the reductant tank has a recess for avoidinginterference with the front wheel.

With the above-aspect of the present invention, a tractor includes: atraveling body having an engine; a post-processing device configured topurify exhaust gas of the engine; and a reductant tank configured tostore a reductant to be supplied to the post-processing device. A pairof left and right fuel tanks are arranged respectively on left and rightsides of a longitudinally midway portion of the traveling body. Atank-accommodation recess for accommodating the reductant tank isformed, at a lower-front portion of one of the left and right fueltanks. While the reductant tank is accommodated in thetank-accommodation recess, an upper front portion of the one of the leftand right fuel tanks and the reductant tank are aligned up and down.This can achieve both: a space for arranging the reductant tank, and thecapacity of one of the left and right fuel tanks or even the capacity ofboth of the fuel tanks, without lengthening the longitudinal length ofthe tractor or sacrificing the size of the operation unit and the step.

Further, in the above-aspect of the present invention, a tractorincluding: a traveling body having an engine; a pair of left and rightfront wheels and a pair of left and right rear wheels to support thetraveling body; steps for getting on and off an operation unit on thetraveling body; a post-processing device configured to purify exhaustgas of the engine; and a reductant tank configured to store a reductantto be supplied to the post-processing device, wherein The reductant tankis arranged between one of the steps and one of the front wheels, on oneof the left and right sides of the traveling body. A front surface ofthe reductant tank has a recess for avoiding interference with the frontwheel. With the recessed of the front surface of the reducing agent, thefront wheel does not interfere with the reductant tank when the frontwheels are steered right or left. The reductant tank can be arranged asclose as possible to the front wheel, and the longitudinal length oftractor and the like can be made compact.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a left side view of a tractor.

FIG. 2 illustrates a right side view of the tractor.

FIG. 3 illustrates a plan view of the tractor.

FIG. 4 illustrates a bottom view of the tractor.

FIG. 5 illustrates a plan view of a traveling body of the tractor.

FIG. 6 illustrates a front view showing an internal structure of thetractor.

FIG. 7 illustrates a perspective view showing a urea water pipingsystem.

FIG. 8 illustrates a rear view showing a support structure of a cabin.

FIG. 9 illustrates a front view showing an arrangement of a left tankand a urea water tank.

FIG. 10 illustrates a left side view showing an arrangement of the lefttank.

FIG. 11 illustrates a plan view showing an arrangement of the urea watertank.

FIG. 12 illustrates a perspective view showing how the urea water tankis attached, as seen from obliquely left rear.

FIG. 13 illustrates a perspective view showing the shape of the frontsurface of the urea water tank, as seen from obliquely left front.

FIG. 14 illustrates a left side view of the left tank and the urea watertank.

FIG. 15 illustrates a right side view of the left tank and the ureawater tank.

FIG. 16 illustrates a plan view of the left tank and the urea watertank.

FIG. 17 illustrates a front view of the left tank and the urea watertank.

FIG. 18 illustrates a rear view of the left tank and the urea watertank.

FIG. 19 illustrates a bottom view of the left tank and the urea watertank.

FIG. 20 illustrates a perspective view of the left tank and the ureawater tank, as seen from obliquely left front.

FIG. 21 illustrates a perspective view of the left tank and the ureawater tank, as seen from obliquely right rear.

DESCRIPTION OF EMBODIMENTS

In the following, an embodiment of the present invention will bedescribed with reference to the drawings. First, a structure of atractor 1 of the present embodiment is described, with reference to FIG.1 to FIG. 6 . A traveling body 2 of the tractor 1 of the presentembodiment is supported by a pair of left and right front wheels 3 and apair of left and right rear wheels 4, as a traveling unit. The tractor 1is structured to travel forward and backward by driving the rear wheels4 and the front wheels 3 by means of a common rail type diesel engine 5(hereinafter, simply referred to as engine) which is mounted in a frontportion of the traveling body 2 and serves as a power source. The engine5 is covered by a hood 6. A cabin 7 (also referred to as operation unit)is installed on an upper surface of the traveling body 2. In an innerportion of the cabin 7, there are arranged an operation seat 8 and asteering handle 9 configured to move a steering direction of the frontwheels 3 right and left by steering. Steps 10 with which an operatorgets on and off the vehicle are provided such that one of them and theother of them are disposed respectively in left and right lower portionsof the cabin 7. A fuel tanks 11 for supplying fuel to the engine 5 isarranged below a bottom portion of the cabin 7.

The traveling body 2 includes: an engine frame 14 including a frontbumper 12 and a front axle case 13; and left and right vehicle bodyframes 15 detachably fixed to a rear portion of the engine frame 14. Afront axle 16 rotatably protrudes outward from both left and right endsof the front axle case 13. The front wheels 3 are attached to both leftand right ends of the front axle casing 13 via the front axle 16. Atransmission case 17 is coupled to the rear portions of the vehicle bodyframes 15. The transmission case 17 suitably shifts the rotary powerfrom the engine 5, and transmits the force to the four front and rearwheels 3, 3, 4, and 4. The left and the right front wheels 3 have uppersides covered with left and right front fenders 26. The left and rightfront fenders 26 are supported above left and right end portions of theupper surface of the front axle case 13.

A tank frame 18 having a rectangular plate shape in bottom view andprotruding outward toward the left and the right is fastened with boltsto an under surface side of the transmission case 17 and the left andthe right vehicle body frames 15. In this embodiment, the fuel tanks 11include two left and right tanks. The left and the right fuel tanks 11are respectively mounted on the upper surface sides of the left and theright protruding portions of the tank frame 18. That is, a pair of leftand right fuel tanks 11 are arranged respectively on the left and rightsides of a longitudinally (i.e., with respect to the front-reardirection) midway portion of the traveling body 2. The tank frame 18extends rightward, and a battery 50 is arranged in an extending portionon the right side of the tank frame 18. Further, to the extendingportion on the right side of the tank frame 18 one of the steps 10 isfixed. Left and right rear axle cases 19 are attached to left and rightouter side surfaces of the transmission case 17 so as to protrudeoutwardly toward left and right, respectively. Left and right rear axles20 are rotatably inserted in the left and the right rear axle cases 19.The rear wheels 4 are attached to the transmission case 17 via the rearaxles 20. The left and the right rear wheels 4 have upper sides coveredwith left and right rear fenders 21.

A hydraulic elevation mechanism 22 that can lift and lower a workmachine (not illustrated), such as a rotary tiller for example, isdetachably attached to an upper surface of the rear portion of thetransmission case 17. The work machine is coupled to the rear portion ofthe transmission case 17 via a three-point link mechanism including apair of left and right lower links 23 and a top link 24. A power-takeoff (PTO) shaft 25 protrudes rearward from a rear side surface of thetransmission case 17 and is used for transmitting a PTO drive force tothe work machine.

As shown in FIG. 5 to FIG. 8 , in an exhaust path of the engine 5, afirst case 31 (also referred to as DPF case) and a second case 32 (alsoreferred to as SCR case) are provided as a post-processing device. Thepost-processing device removes particulate matter (e.g., soot and thelike) and nitrogen oxides (NOx) contained in the exhaust gas of theengine 5, and discharges purified exhaust gas to the outside. In thepresent embodiment, the first case 31 accommodates therein an oxidationcatalyst and a soot filter (not shown). In the second case 32, an SCRcatalyst for urea selective catalytic reduction and an oxidationcatalyst (not shown) are accommodated. The first case 31 is mounted atan upper portion of the engine 5, along a crank axis direction (in thefront-rear direction, in the present invention). The second case 32 isarranged on the lower right portion of the front portion of the cabin 7,in a standing posture such that the exhaust gas flows from the bottom tothe top.

An exhaust gas outlet side of the first case 31 is connected to anexhaust gas inlet side of a purification outlet pipe 33 which is long ina front-rear direction. In a midway portion of the purification outletpipe 33 relative to its length direction, a bellows portion 34 forvibration absorption is provided. An exhaust gas outlet side of thepurification outlet pipe 33 is coupled to an exhaust gas inlet side(upper end side) of a urea mixing pipe 35. The urea mixing pipe 35 has asubstantially L-shape, which extends upward from a lower side on a rightfront side of the cabin 7, and at a lower side of the cabin 7 benttoward a direction away from the engine 5. An exhaust gas outlet side(lower end side) of the urea mixing pipe 35 is coupled to a lower sideof a left side portion of the second case 32. The exhaust gas outletside of the purification outlet pipe 33 and the exhaust gas inlet sideof the urea mixing pipe 35 are coupled to the engine 5 through a flange.The engine 5 supports the exhaust gas outlet side of the purificationoutlet pipe 33 and the exhaust gas inlet side of the urea mixing pipe35. An under surface side of the second case 32 is coupled to alater-described right front-portion support pedestal 96 through a casesupport bar 48. The exhaust gas having passed through the first case 31is introduced into the second case 32 through the purification outletpipe 33 and the urea mixing pipe 35.

To an upper end side of the urea mixing pipe 35, a urea water injectionunit 36 is attached. Urea water (reductant) in a later-described ureawater tank 51 (reductant tank) is supplied from the urea water injectionunit 36 into the urea mixing pipe 35, and the urea water is hydrolyzedand mixed as ammonia, into the exhaust gas from the first case 31 to thesecond case 32. It should be noted that other reductant, e.g., ammoniaor ammonia water may be used instead of urea water.

On the right side of the front portion of a box-frame-like cabin frame37 constituting the cabin 7, an assist bar 38 is provided. The assistbar 38 is coupled to a plurality of positions of a tail pipe 39 which islong in an up-down direction, and which emits the exhaust gas to theoutside. The tail pipe 39 is supported by the assist bar 38. An exhaustgas outlet side (upper surface side) of the second case 32 is connectedto and in communication with an exhaust gas inlet side of the tail pipe39. The exhaust gas of the engine 5 is purified by the first case 31 andthe second case 32 and is emitted to the outside the machine through thetail pipe 39.

In the above structure, particulate matters (PM), carbon monoxide (CO),and hydrocarbon (HC) in the exhaust gas of the engine 5 are firstreduced by the oxidation catalyst and the soot filter in the first case31. In the inside of the urea mixing pipe 35, the urea water from theurea injection unit 36 is mixed with the exhaust gas having passedthrough the first case 31, and the nitrogen oxide (NOx) in the exhaustgas in which the urea water is mixed as ammonia is reduced by the SCRcatalyst and oxidation catalyst in the second case 32. Then, the exhaustgas having passed through the second casing 32 is discharged to theoutside of the machine from the tail pipe 39.

As shown in FIG. 4 and FIG. 5 , a fuel tank 11 includes a left tank 11Land a right tank 11R arranged below the cabin 7, and inward from a pairof left and right steps 10 and the rear wheels 4 (on the side of thevehicle body frames 15). The left tank 11L and the right tank 11R arearranged respectively on the left and right so as to sandwich the pairof vehicle body frames 15. That is, a front portion of the left tank 11Lis arranged between the left vehicle body frame 15 and the left step 10,while a rear portion of the left tank 11L is arranged between the leftvehicle body frame 15 and the left rear wheel 4. Similarly, a frontportion of the right tank 11R is arranged between the right vehicle bodyframe 15 and the right step 10, while a rear portion of the right tank11L is arranged between the right vehicle body frame 15 and the rightrear wheel 4. The respective capacities of the left tank 11L and theright tank 11R are different from each other. The left and right tanks11L, 11R communicate with each other through a fuel communication tube(not shown) at lower portions of their surfaces facing inward. The lefttank 11L with a large capacity protrudes forward from the left step 10at the front of the cabin 7. In other words, the left tank 11L is formedso as to surround the right side and the front side of the left step 10.

The fuel tank 11 is placed on the tank frame 18 outwardly protrudingtoward left and right below the vehicle body frames 15, and fixed by aband 40. The tank frame 18 is formed in a rectangular plate shape in abottom view, with: a front lateral bridge frame 41 suspended and fixedto the left and right vehicle body frames 15; a rear lateral bridgeframe 42 fixed to an under surface of the transmission case 17; and leftand right tank mounting plates 43 fixed on both ends of the lateralbridge frames 41, 42. The shapes of the left and right tank mountingplates 43 are substantially the same as the shapes of the bottom surfaceof the left tank 11L and the right tank 11R, respectively, and the lefttank 11L and the right tank 11R placed on the upper surfaces of the tankmounting plates 43 are fixed by bands 40 at two positions that are thefront and the rear.

As described, the tank frame 18 is constituted by the pair of front andrear lateral bridge frames 41, 42 extending left and right below theleft and right vehicle body frames 15, and the pair of left and righttank mounting plates 43 bridged in the front-rear direction, on bothleft and right sides of the front and rear lateral bridge frames 41, 42.On the left and right tank mounting plates 43, the right and left fueltanks 11L, 11R are placed and fixed, respectively.

As shown in FIG. 1 to FIG. 5 , the steps 10 for the operator to get onand off the vehicle are provided at lower portions on the left and rightsides of the cabin 7. As shown in FIG. 8 , the left step 10 is arrangedto stand on the left end side of the front lateral bridge frame 41. Tothe upper end side of the left step 10, a left front-portion supportpedestal 96 is attached. The left step 10 of the present embodimentincludes two steps of foot plate members 44, 45, which are an upper anda lower foot plate members; and front and rear side plate members 46coupled to these foot plate members 44, 45. The lower foot plate member45 is fastened to the left end side of the front lateral bridge frame41. To the upper end sides of the front and rear side plate members 46,the left front-portion support pedestal 96 is fastened. A portion of theleft tank 11L close to its front portion is fitted in a space surroundedby the left front-portion support pedestal 96, the left step 10, and thefront lateral bridge frame 41. To the right end side of the frontlateral bridge frame 41, a lower foot plate member 45 constituting theright step 10 is fastened. The right step 10 includes the lower footplate member 45 and an upper step plate member 44 coupled to a lowerright portion of the cabin frame 37.

To a portion close to the right of the front lateral bridge frame 41, astanding support column 47 is provided. To the upper end side of thestanding support column 47, the right front-portion support pedestal 96is attached. In a space surrounded by the right front-portion supportpedestal 96, the standing support column 47, and the front lateralbridge frame 41, a front portion of the right tank 11R is fitted. On theupper surface sides of the left and right front-portion supportpedestals 96, a front bottom portion of the cabin 7 is supported, in avibration controlled manner, through a vibration rubber member 98. Onthe front surface side of the right front-portion support pedestal 96, acase support bar 48 long in the left-right direction is fastened. To theupper surface on the right outer side of the case support bar 48, theunder-surface side of the second case 32 is fastened. The second case 32is supported by the right front-portion support pedestal 96 through thecase support bar 48. Each of the left and right rear axle cases 19extended horizontally in the left-right direction has, on its uppersurface, a rear portion support pedestal 97 fastened to a middle portionof the upper surface relative to the left-right width. On the uppersurface side of each of the left and right rear portion supportpedestals 97, a rear bottom portion of the cabin 7 is supported, in avibration controlled manner, through an anti-vibration rubber member 99.Therefore, the traveling body 2 supports the cabin 7 in a vibrationcontrolled manner, through the anti-vibration rubber members 98, 99.

A battery seat 49 is attached to a midway portion of the standingsupport column 47 relative to the up-down direction. The battery 50 ismounted on the battery seat 49. In the embodiment, the battery 50 islocated below the second case 32, and the lower foot plate member 45 ofthe right step 10 is located on the right outside of the battery 50.

As shown in FIG. 9 to FIG. 11 , in a lower-front portion of the lefttank 11L, a tank-accommodation recess 52 for accommodating the ureawater tank 51 (reductant tank) is formed. The urea water tank 51 is abox-like member for containing urea water (urea water solution forselective catalytic reduction). An upper front portion 11LF of the lefttank 11L and the urea water tank 51 are aligned up and down, while theurea water tank 51 is accommodated in the tank-accommodation recess 52.This can achieve both: a space for arranging the urea water tank 51, andthe capacity of the left tank 11L or even the capacities of both of theentire fuel tank 11, without lengthening the longitudinal length of thetractor 1 or sacrificing the size of the cabin 7 (operation unit) andthe step 10.

An auxiliary frame 53 extended toward the left tank 11L having thetank-accommodation recess 52 is provided to the traveling body 2. Inthis case, one end side of the auxiliary frame 53 is fastened to theleft engine frame 14. The other end side of the auxiliary frame 53 fixesa tank seat 54 having a flat plate shape. The tank seat 54 is fastenedto the left end side of the front lateral bridge frame 41 constitutingthe tank frame 18.

To the bottom surface and the rear surface of the urea water tank 51, aninsert nut (not shown) is embedded. The bottom surface of the urea watertank 51 and the tank seat 54 are fastened with a bolt and the insert nutand the rear surface of the urea water tank 51 and a front side platemember 46 of the left step 10 are fastened with a bolt and the insertnut, while the urea water tank 51 is accommodated in thetank-accommodation recess 52 (see FIG. 4 and FIG. 12 ). With the leftstep 10 and the auxiliary frame 53, the urea water tank 51 is stablyfixed and supported.

On the upper surface of the upper front portion 11LF of the left tank11L, a fueling cylinder 55 protrudes upward. On the left outer sidesurface of the urea water tank 51, a supply cylinder 56 protrudesobliquely upward and outward. As described, since the direction in whichthe fueling cylinder 55 protrudes and the direction in which a supplycylinder 56 are different from each other, the fuel and the urea watercan be supplied from the same side (left side) of the traveling body 2,and yet mistakes in supplying wrong one of the fuel and the urea waterbecomes less likely to occur. Particularly, in this embodiment, thefueling cylinder 55 for the fuel which is more frequently supplied ispositioned above the supply cylinder 56 for the urea water. Therefore,the risk of mistakenly supplying fuel to the supply cylinder 56 of theurea water tank 51 is reduced.

As shown in FIG. 13 , the front surface of the urea water tank 51 has arecess 57 to avoid interference with the left front wheel 3 (including aleft front fender 26). The recess 57 of this embodiment is a recessfacing forward which is concaved along the outer circumference shape ofthe left front wheel 3 (including the left front fender 26). With therecess 57 on the front surface of the urea water tank 51, the left frontwheel 3 hardly interfere with the urea water tank 51 when the frontwheels 3, 3 are steered left and right. Thus, the urea water tank 51 canbe arranged as close as possible to the left front wheel 3, and thelongitudinal length of the tractor 1 and the like can be made compact.

As shown in FIG. 7 and FIG. 8 , the engine 5 (cooling water pump) andthe urea water injection unit 36 are in communication with each otherthrough a cooling water feed pipe 101 and a cooling water return pipe102. One ends of the cooling water feed pipe 101 and the cooling waterreturn pipe 102 are connected to the engine 5 (cooling water pump). Theother ends of the cooling water feed pipe 101 and the cooling waterreturn pipe 102 are connected to the urea water injection unit 36. Thecooling water feed pipe 101 and the cooling water return pipe 102 areconnected in the urea water injection unit 36. The cooling water heatedby the engine 5 is fed from the cooling water feed pipe 101 to thecooling water return pipe 102 through the urea water injection unit 36,thus keeping the urea water from being frozen in the urea waterinjection unit 36. The cooling water having passed through the ureawater injection unit 36 is returned to the engine 5 (cooling water pump)through the cooling water return pipe 102.

A cooling water supply pipe 103 is branched from a middle portion of thecooling water feed pipe 101. The cooling water supply pipe 103 isconnected to a tank sensor unit 58 attached to the urea water tank 51.In this case, an indentation 51 a which is a recess opened upward isformed on the upper surface side of the urea water tank 51. An upwardprotrusion 5 lb on the upper surface side of the urea water tank 51 isin contact with the bottom surface of the upper front portion 11LF inthe left tank 11L through an L-shaped buffer member 59. The tank sensorunit 58 is detachably attached to an upper surface opening of theindentation 51 a of the urea water tank 51. The tank sensor unit 58 alsofunctions as a lid of the upper surface opening. The tank sensor unit 58is connected to the cooling water supply pipe 103, a cooling watercollection pipe 104, a urea water feed pipe 105, a urea water returnpipe 106, and the like.

The cooling water supply pipe 103 and the cooling water collection pipe104 are connected in the urea water tank 51. The cooling watercollection pipe 104 is connected to the engine 5 (cooling water pump).The cooling water heated by the engine 5 is fed from the cooling watersupply pipe 103 to the cooling water collection pipe 104 through theurea water tank 51, thus keeping the urea water from being frozen in theurea water tank 51. The cooling water having passed through the ureawater tank 51 is returned to the engine 5 (cooling water pump) throughthe cooling water collection pipe 104.

The other ends of the urea water feed pipe 105 and the urea water returnpipe 106 whose one ends are connected to the tank sensor unit 58 areconnected to a urea water supply device 107 (supply module, reductantsupply device) configured to supply urea water in the urea water tank 51to the urea water injection unit 36 of the urea mixing pipe 35. The ureawater supply device 107 is connected to the urea water injection unit 36through a urea water injection pipe 108. The urea water supply device107 sucks the urea water in the urea water tank 51 through the ureawater feed pipe 105, and supplies the urea water to the urea waterinjection unit 36 through the urea water injection pipe 108, to spraythe urea water in the urea mixing pipe 35. The surplus urea water isreturned to the urea water tank 51 through the urea water return pipe106.

As shown in FIG. 9 to FIG. 11 , the urea water supply device 107 isarranged between the traveling body 2 and the urea water tank 51.Although details are omitted, the urea water supply device 107 includesa urea water pump configured to pressure-feed the urea water in the ureawater tank 51, and a drive motor configured to drive the urea waterpump. By the urea water supply device 107 supplying the urea water inthe urea water tank 51 to the urea water injection unit 36 of the ureamixing pipe 35, the urea water is sprayed from the urea water injectionunit 36 into the urea mixing pipe 35. In this case, the urea watersupply device 107 is arranged on the tank seat 54 between the leftvehicle body frame 15 and the urea water tank 51. Thus, a dead spacebetween the traveling body 2 (left vehicle body frame 15) and the ureawater tank 51 is effectively used as a space for arranging the ureawater supply device 107. Therefore, the distance of the urea waterpiping system from the urea water tank 51 to the urea water injectionunit 36 of the urea mixing pipe 35 through the urea water supply device107 can be shortened.

As shown in FIG. 10 and FIG. 11 , the tank sensor unit 58 of the ureawater tank 51 is connected to one end of a breather pipe 109 forrelieving the pressure of the urea water tank 51. The other end of thebreather pipe 109 is branched into two branches. One of the branchedpipe portions 109 a is extended upward and opened. The other one of thebranched pipe portions 109 b is extended downward and opened at a midwayof the traveling body 2 relative to the left-right direction (furtherinward than the front and rear wheels 3 and 4, relative to theleft-right direction). Therefore, the pressure in the urea water tank 51is kept constant by introducing outside air through the upward pipeportion 109 a of the breather pipe 109, at a time of supplying the ureawater. For example, even if the vibration of the engine 5 or shaking ofthe urea water tank 51 caused by unevenness of the field causes the ureawater to enter the breather pipe 109, the urea water drops from thedownward pipe portion 109 b of the breather pipe 109. Therefore,clogging of the upward pipe portion 109 a caused by, for example,adhesion and deposition of the urea can be avoided. Therefore, smoothintroduction of the outside air can be reliably performed through thebreather pipe 109.

It goes without saying that the positional relationship among thetank-accommodation recess 52, the urea water tank 51, and the secondcase 32 is not limited to the example mentioned in this embodiment, andthe left and right sides may be reversed. In such a case, the positionalrelationship among the battery 50, the left and right fuel tanks 11, thesteps 10, and the like are also reversed.

The configurations of respective parts of the present invention are notlimited to those of the illustrated embodiment, but can be variouslychanged without departing from the gist of the invention.

REFERENCE SIGNS LIST

-   1 tractor-   2 traveling body-   5 diesel engine-   7 cabin-   10 step-   11 fuel tank-   11L left tank-   11LF upper front portion of left tank-   11R right tank-   18 tank frame-   31 first case-   32 second case-   35 urea mixing pipe-   36 urea water injection unit-   39 tail pipe-   51 urea water tank-   52 tank-accommodation recess-   55 fueling cylinder-   56 supply cylinder-   57 recess-   58 tank sensor unit-   107 urea water supply device

1. A tractor comprising: a traveling body having an engine; a pair ofleft and right front wheels and a pair of left and right rear wheels tosupport the traveling body; steps for getting on and off an operationunit on the traveling body; a fuel tank that supplies fuel to theengine; a post-processing device configured to purify exhaust gas of theengine and a reductant tank configured to store a reductant to besupplied to the post-processing device, wherein: the reductant tank isarranged on either the left or right side of the traveling body, and infront of the steps; the front wheels are arranged in front of thereductant tank; and a recess is formed on the front surface of thereductant tank.
 2. The tractor according to claim 1, wherein the recessis being recessed in a forward-facing concave shape along an outerperipheral shape of the front wheel.
 3. The tractor according to claim1, wherein: a fender is provided on the front wheels; and the recess isformed on the front surface of the reductant tank and on a side wherethe fender is provided.
 4. The tractor according to claim 1, wherein afueling cylinder of the fuel tank is provided in front of the steps andabove the recess of the reductant tank.
 5. The tractor according toclaim 1, wherein a replenishing cylinder of the reductant tank isprovided facing obliquely upward and outward behind the recess of thereductant tank and on the left and right outer side surfaces of thereductant tank.
 6. The tractor according to claim 1, wherein a fuelsupply cylinder of the fuel tank and a replenishment cylinder of thereductant tank are arranged side by side in the width direction of thetraveling body.